JP2001031769A - Production of emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently produce an O/W emulsion having a specified average particle size or smaller by a simple process with a simple apparatus by constituting a circulation system of an emulsifying vessel and a high-pressure homogenizer, and by charging an oil phase and a water phase at a specified wt. ratio into the emulsifying vessel and then mixing them under circulation while the oil phase is being added to the emulsifying vessel. SOLUTION: An oil phase and a water phase in a wt. ratio of oil phase/water phase of (0/100)-(40/60) are charged into an emulsifying vessel to produce an O/W emulsion having an average particle size of 1 μm or smaller. The oil phase and the water phase are separately charged into the emulsifying vessel without using a pre- emulsifying apparatus. Premixing after the oil phase and the water phase are charged is preferable, since the emulsifying time can be decreased in the mixing under circulation. It is sufficient if the premixing is done under unvigorous stirring by using an anchor blade or the like. Preferably, the addition of the oil phase is completed at an O/W ratio of at most (60/40). The addition in the case when the mixing under circulation is done while the oil phase is being added may be carried out by any method other than the addition at one time, though the rate of addition is preferably not higher than the rate of liquid transportation by the high-pressure homogenizer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an O / W emulsion having an average particle size of 1 μm or less with simple equipment and simple steps.

[0002]

2. Description of the Related Art O / W emulsions having a smaller particle diameter than ordinary O / W emulsions and having an average particle diameter of 1 μm or less sometimes show better performance than ordinary O / W emulsions. For example, when the pressure-sensitive adhesive is 1 μm or less, the water whitening resistance is good. As a method for preparing an O / W emulsion having an average particle size of 1 μm or less, there are a method of using a large amount of a dispersant and utilizing the interfacial properties of the dispersant and a method of mechanically applying a large crushing energy.

The former method includes a solubilization method and a phase inversion emulsification method. In the latter method, a high-shear homomixer or a high-pressure homogenizer is used as an emulsifier having larger crushing energy than a conventional chemical stirrer, homomixer or the like. Here, a system in which a large amount of a dispersant cannot be used due to restrictions on human body safety, economy, and product performance, for example, a dispersion system such as an emulsion-type pressure-sensitive adhesive composition disclosed in JP-A-7-330813. For systems in which the amount of the agent used has an upper limit, a method in which a small amount of a dispersant is used and the latter method is used in combination is suitable, but it is difficult to obtain a stable emulsion. Even if an O / W emulsion is obtained, the phase may be further changed to a W / O emulsion or demulsification may occur during the standing. Further, demulsification can easily occur even in a system having a large oil phase / water phase ratio (weight ratio) (hereinafter referred to as an O / W ratio) (O / W ratio of 40/60 to 60/40).

In order to stably obtain an O / W emulsion having an average particle diameter of 1 μm or less, an oil phase and an aqueous phase are separately supplied to a homomixer or the like in advance and pre-emulsified to about 1 to 10 μm, and then a high-pressure homogenizer is used. There is a method of obtaining the desired emulsion by emulsification by passing through (JP-A-6-206934), but a pre-emulsification facility is required, and the process time becomes longer by the pre-emulsification time.

[0005] Without using a preliminary emulsification equipment, a circulation system is formed by an emulsification tank and a pipeline mixer, and an oil phase and an aqueous phase are separately added to the emulsification tank at a ratio of 60/40 or less, and then premixed. Therefore, even if the mixture is emulsified by circulation and mixing, an O / W emulsion having an average particle size of 1 μm or less cannot be obtained. Even if a high shear homomixer is used instead of a pipeline mixer, an O / W emulsion having an average particle size of 1 μm or less cannot be obtained.

[0006]

The present invention provides an O / W ratio of 0 /
A system having a large O / W ratio of 100 to 60/40 (O / W ratio 40
/ 60 to 60/40), but stable O /
An object of the present invention is to provide a method for producing an O / W emulsion having an average particle size of 1 μm or less, which can efficiently produce a W emulsion with simple equipment and simple steps.

[0007]

That is, in the present invention, a circulation system is formed by an emulsifying tank and a high-pressure homogenizer, and an oil phase and an aqueous phase are added to the emulsifying tank at an O / W ratio of 0/100 to 40/60. Then
Circulating and mixing while adding the oil phase to the emulsification tank
m or less.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A circulation system is formed by an emulsification tank and a high-pressure homogenizer, and an oil phase and an aqueous phase are used without using a pre-emulsification equipment.
The oil phase and the aqueous phase are separately added to the emulsification tank at an O / W ratio of 0/100 to 60/40. Premixing after adding the oil phase and the aqueous phase is preferable because the emulsification time in circulation mixing can be shortened. The pre-mixing may be performed by using an anchor blade or the like with stirring that is not intense.

The oil phase and the aqueous phase are added to the emulsification tank at an O / W ratio of 0/100, that is, the O / W ratio exceeds 0/100 (0/100 is not included), Addition of 60 or less is preferable because the addition time of the oil phase can be shortened.

From the viewpoint of exhibiting the excellent effect of the present invention of obtaining a stable O / W emulsion having an average particle diameter of 1 μm or less, the addition of the oil phase is preferably completed at an O / W ratio of 60/40 or less. The / W ratio is more preferably from 40/60 to 60/40.

The addition in the case of circulating mixing while adding the oil phase may be any of dropping, continuous addition, divided addition and intermittent addition, other than batch addition, but the addition speed is not higher than the liquid sending speed of the high-pressure homogenizer. preferable. It is preferable that the addition of the oil phase be completed when the average particle size becomes 1 μm or less.

Examples of the high-pressure homogenizer include “Fragrance Journal” (1993, April 57, p. 57) and “Food Chemical” (1988, April 82)
Page), a pressure mechanism for obtaining the processing pressure and a valve mechanism for obtaining the crushing effect. A pressure is applied to the sample, and the sample is atomized when passing through the gap between the valve and the valve seat. Described in JP-A-6-206934 and the pre-emulsified mixed liquid is introduced into the flow path in the chamber under pressure, and the mixed liquid is caused to collide with a flat portion in the flow path under high pressure, Alternatively, a device for emulsifying the mixture by causing the mixture to collide with each other in the flow path under high pressure may be used. As a representative device of the above-mentioned devices, a high-pressure homogenizer (R
Annie, Gaulin, Sanmaru Kikai Co., Ltd.), high-pressure homogenizer (Izumi Food Machinery Co., Ltd.), and microfluidizer (Mic
rofluidics), Nanomizer (Nanomizer Co., Ltd.)
And the like. From the viewpoint of obtaining an emulsion having an average particle size of 1 μm or less, the pressure is preferably from 9.8 to 196 MPa, and 19.6 to 196 MPa.
150150 MPa is more preferred.

In the emulsification tank, the oil phase and the aqueous phase are added at an oil phase / aqueous phase ratio (weight ratio) of 0/100 to 40/60, and then mixed. A stirrer can be provided for mixing. If a high-pressure homogenizer having a liquid sending capacity of sending the liquid in the emulsification tank within one hour is used, emulsification may be performed without stirring, and energy for operating the stirrer may be unnecessary, or an emulsification tank without a stirrer may be used. It is preferable because it can be used and the emulsification tank becomes simple.

As the oil phase component of the O / W emulsion, 2
Organic compounds having a solubility in water at 0 ° C. of 1% or less are preferred. Such organic compounds include cyclohexane,
n-hexane, benzene, cottonseed oil, rapeseed oil, squalane, squalene, wax, lipophilic polymerizable monomer,
An organic solvent solution of a polymer compound obtained by polymerizing a lipophilic polymerizable monomer and a polymer compound obtained by polymerizing a lipophilic polymerizable monomer can be used. As lipophilic polymerizable monomers, styrene, divinylbenzene, butyl acrylate,
(Meth) acrylates such as cyclohexyl acrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate; and silicone macromonomers.
As the oil phase component, one or more of the above oil phase components can be used. When an organic solvent solution of a polymer compound is used, the organic solvent may be removed from the obtained O / W emulsion.

Examples of the dispersant include anionic surfactants such as dodecyl sulfate, dodecylbenzenesulfonate, sulfate salt of polyoxyethylene nonylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, and fatty acid salt. Nonionic surfactants such as sugar esters, cationic surfactants such as octadecyltrimethylammonium chloride, amphoteric surfactants such as betaine alkyldimethylaminoacetate, and 2-alkyl-N-carboxy-N-hydroxyimidazolinium betaine; Natural or synthetic polymers such as gelatin, hydroxyalkylcellulose, polyvinyl alcohol, and acrylic resins are exemplified. One or more of these dispersants are used. The amount of the dispersant used is preferably 0.1 to 10% by weight based on the oil phase of the final composition, and 1 to 10% by weight.
5% by weight is more preferred. The amount used is preferably an amount that does not adversely affect the required properties of the product.

A polymer emulsion can also be obtained by using the lipophilic polymerizable monomer as the oil phase and emulsifying in the presence of an oil-soluble polymerization initiator to polymerize the resulting emulsion. The oil-soluble polymerization initiator is one that initiates addition polymerization of a monomer by radical decomposition in the presence of heat or a reducing substance, and generally includes oil-soluble peroxides and azobis compounds. Examples thereof include organic peroxides such as lauroyl peroxide and benzoyl peroxide, and azo compounds such as 2-2'-azobisisobutyronitrile and 2-2'-azobis (2,4-dimethylvaleronitrile). . One or more of these polymerization initiators can be used.

The polymer emulsion has a stable average particle size.
Although it is often difficult to obtain an O / W emulsion of 1 μm or less, the method of the present application is suitably used for producing the polymer emulsion. As the polymer emulsion, a polymer emulsion obtained by using the above-described lipophilic polymerizable monomer and polymerizing an emulsion formed by emulsification in the presence of an oil-soluble polymerization initiator, a polymer compound obtained by polymerizing a lipophilic polymerizable monomer And a polymer emulsion of a solution of the polymer compound in an organic solvent.

[0018]

EXAMPLES Examples and comparative examples were performed at 25 ° C. unless otherwise specified. The average particle size of the emulsion was determined by the following method, and the results are shown in Examples and Comparative Examples. Apparatus name: Laser diffraction /
Scattering type particle size distribution analyzer LA910, Manufacturer: HORIBA, Refractive index: 1.20, Transmittance: 89% ~ 91%, Conversion type: Volume weight distribution

Example 1 997 kg of lauryl methacrylate (LMA) and 3 kg of benzoyl peroxide (75% BPO) having an active ingredient concentration of 75% were added to a 2 m ³ addition tank and dissolved to obtain an oil phase component of 1000 kg. 3m ³ emulsification tank and a high-pressure homogenizer: forming a circulatory system with (feeding capacity 500 L / h, Sanmaru Machinery Co., Ltd.), an aqueous phase component which is circulated mixed at a pressure of 19.6 MPa (LATEMUL S180 (oleyl 2-hydroxy (3
An oil phase component was added to 800 kg of a 2 wt% aqueous solution of allyloxy) propiosulfosuccinate Na salt (manufactured by Kao Corporation) over 1 hour to emulsify. The O / W ratio at the end of the oil phase addition was 56/44. After completion of the addition, the O / W emulsion obtained by emulsifying the mixture by performing circulation three more times has an average particle size of 0.1.
It was 5 μm. Here, the mixing in the emulsification tank was performed at 40 rpm using an anchor blade. Further, a part of this O / W emulsion was polymerized at 75 to 80 ° C. for 6 hours to obtain a polymer emulsion.

Comparative Example 1 The same oil phase component (1000 kg) and aqueous phase component (800 kg) as in Example 1 were used.
The mixture was previously stirred and mixed in a ³ m3 emulsification tank to obtain an emulsion of 120 μm. Stir and mix in the emulsification tank using an anchor blade.
m. Next, the emulsion was circulated in the same circulation system as in Example 1 at a pressure of 19.6 MPa to emulsify. The O / W ratio at the end of the oil phase addition was 56/44. The resulting emulsion is W / O type and unstable, and O / W
No emulsion was obtained.

Example 2 The same oil phase component as in Example 1 (1000 kg) was prepared in a 2 m ³ addition tank. 530 Kg of this oil phase component and 800 of the same water phase component as in Example 1.
Kg (O / W ratio 40/60) was previously stirred and mixed in a ³ m3 emulsification tank. Mixing was performed at 40 rpm using anchor blades.
Next, the same circulation system as in Example 1 was circulated at a pressure of 19.6 MPa, and 470 kg of the remaining oil phase component was added over 30 minutes to emulsify. The O / W ratio at the end of the oil phase addition was 56/44. After completion of the addition, the O / W emulsion obtained by emulsification by performing circulation three more times had an average particle size of 0.6 μm.

Example 3 A 2 m ³ addition tank was added to a 1 m ³ addition tank, a 3 m ³ emulsification tank to a 1 m ³ emulsification tank, an oil phase component to 300 kg, and an aqueous phase component to 240 kg, and mixing in the emulsification tank was not performed. Otherwise in the same manner as in Example 1, an emulsion having an average particle size of 1 μm or less was obtained.

[0023]

Since pre-emulsification is unnecessary, a stable emulsion having an average particle size of 1 μm or less can be easily obtained with simple equipment that does not require a pre-emulsification tank or a pre-emulsification step.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Kubo 1334 Minato 1334 Minato, Wakayama City, Wakayama Prefecture (72) Inventor Yasuhisa Otani 1334 Minato 1 Minato, Wakayama City, Wakayama Prefecture F-term (reference) 4F070 AA17 AA32 AA60 AA71 AC43 AC50 AC72 AC80 AC83 AE14 CA02 CB13 4J011 AA01 DA01 KA04 KA08 KA10 KA15 KA16 KA17 KB30

Claims (4)

[Claims] 1. A circulation system is formed by an emulsification tank and a high-pressure homogenizer, and an oil phase and an aqueous phase are added to the emulsification tank at an oil phase / water phase ratio (weight ratio) of 0/100 to 40/60. A method for producing an O / W emulsion having an average particle size of 1 μm or less, which is circulated and mixed while adding an oil phase to a tank. 2. The method according to claim 1, wherein the oil phase / water phase ratio (weight ratio) at the end of the addition of the oil phase is 60/40 or less. 3. The method according to claim 1, wherein the oil phase / water phase ratio (weight ratio) at the end of the addition of the oil phase is 40/60 to 60/40. 4. The method according to claim 1, wherein the O / W emulsion is an O / W polymer emulsion.